AUTHOR=Wang Jiaxue , Rao Lulin , Huang Zhuoan , Ma Lili , Yang Tian , Yu Zhongqi , Sun Aihua , Ge Yumei 

TITLE=The nitric oxide synthase gene negatively regulates biofilm formation in Staphylococcus epidermidis

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=12

YEAR=2022

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2022.1015859

DOI=10.3389/fcimb.2022.1015859

ISSN=2235-2988

ABSTRACT=<p><italic>Staphylococcus epidermidis (S. epidermidis)</italic> is a clinically important conditioned pathogen that can cause a troublesome chronic implant-related infection once a biofilm is formed. The nitric oxide synthase (<italic>NOS</italic>) gene, which is responsible for endogenous nitric oxide synthesis, has already been found in the genome of <italic>S. epidermidis</italic>; however, the specific mechanisms associated with the effects of <italic>NOS</italic> on <italic>S. epidermidis</italic> pathogenicity are still unknown. The purpose of the current study was to investigate whether the <italic>NOS</italic> gene has an impact on biofilm formation in <italic>S. epidermidis</italic>. Bioinformatics analysis of the <italic>NOS</italic> gene was performed, and homologous recombination was subsequently employed to delete this gene. The effects of the <italic>NOS</italic> gene on biofilm formation of <italic>S. epidermidis</italic> and its underlying mechanisms were analyzed by bacterial growth assays, biofilm semiquantitative determination, Triton X-100-induced autolysis assays, and bacterial biofilm dispersal assays. Additionally, the transcription levels of <italic>fbe</italic>, <italic>aap</italic>, <italic>icaA</italic>, <italic>icaR</italic> and <italic>sigB</italic>, which are related to biofilm formation, were further investigated by qRT-PCR following <italic>NOS</italic> deletion. Phylogenetic analysis revealed that the <italic>NOS</italic> gene was conserved between bacterial species originating from different genera. The <italic>NOS</italic> deletion strain of <italic>S. epidermidis</italic> 1457 and its counterpart were successfully constructed. Disruption of the <italic>NOS</italic> gene resulted in significantly enhanced biofilm formation, slightly retarded bacterial growth, a markedly decreased autolysis rate, and drastically weakened bacterial biofilm dispersal. Our data showed that the <italic>fbe</italic>, <italic>aap</italic> and <italic>icaA</italic> genes were significantly upregulated, while the <italic>icaR</italic> and <italic>sigB</italic> genes were significantly downregulated, compared with the wild strain. Therefore, these data strongly suggested that the <italic>NOS</italic> gene can negatively regulate biofilm formation in <italic>S. epidermidis</italic> by affecting biofilm aggregation and dispersal.</p>